Isolation, purification, and biochemical characterization of factors which promote growth and differentiation of myelogenous leukemia cells and T-cells. Sources actively producing such factors will be provided by the Government. Development of assay systems for the selective growth of leukemic leukocytes as compared to normal bone cells and evaluation of such selective growth systems for detecting the presence of residual leukemic cells in remission patients and exploration of the use of such growth systems for developing in vitro assay systems for leukocyte transformation.